A Highly Convenient Synthesis of Hydroxytyrosol and Its Recovery from Agricultural Waste Waters

Hydroxytyrosol, a polyphenol with very interesting antioxidant properties, which naturally occurs in virgin olive oil and mainly in olive oil mill waste waters, was synthesized by reducing 3,4-dihydroxyphenylacetic acid with LiAlH4 in tetrahydrofuran under refluxing for 2 h. The yield of reaction was 82.8%. The spectroscopic and HPLC data of the synthesized compound proved to coincide fully with those of a pure sample obtained by the chromatographic recovery from olive oil mill waste waters (yield = 91 mg/L). This synthetic method appears to be the most convenient compared with those reported in the literature and is more convenient than the chromatographic recovery. The tri- and diacetyl derivatives of the synthetic compound were also prepared for structure−bioactivity relationship studies. A brief discussion is given on the economical and ecological aspects regarding the production of hydroxytyrosol. Keywords: Olea europea; olive oil mill waste waters; hydroxytyrosol; acetyl derivatives; antioxidant polyphenol; synthesis; HPLC analysis; spectroscopy; chromatography